FIG. 2.

Effect of culture temperature on supercoiled circular DNA. Plasmid DNAs from bacteria grown at 23 or 34°C were separated on agarose gels containing either 0, 3, 9, or 12 μg of chloroquine/ml, followed by Southern blot analysis. Each experiment was repeated twice, and arrows indicate supercoiled (SC) DNA. In some panels, linearized plasmid is also visible. Top row, membranes probed with probe derived from ORF3-ORFC region encoded on cp32-1 (15), which is specific for that plasmid. Middle row, membranes probed with the generic cp32 probe 2, which recognizes every erp promoter region (26). Lowest row, membranes probed with probe 3, derived from the ospC promoter region of cp26 (6).